Analysis of cavitation performances of an axial flow tandem pump based on computational fluid dynamics

Computations of the cavitating flows in an axial flow tandem pump are conducted to analyze the cavitation performances. FBM turbulence model is adopted to close governing equations, which combines RANS and LES together. Turbulent model is introduced to the CFX commercial code using re-developing method. Zwart cavitation model is used to process the mass transfer in the cavitation process. Cavitating flows in a conventional axil flow pump are calculated to get the model validation and predicted cavitation performance compared well with experimental data. The results of tandem pump demonstrate that with the decrease of available net positive suction head (NPSHa), the cavitation development in tandem pump can be divided into four stages: Inception cavitation, developing cavitation in front impeller, developing cavitation in back impeller and developed cavitation in the whole pump. During the second and third stages, transitional energy performances of the tandem pump can be observed. In this transitional process, no obvious decrease for the head and efficiency of the tandem pump can be observed. It's because the energy performance of the back impeller increases slightly while that of the front impeller decreases.